Spatial Memory Organized by Environmental Geometry

We investigated the simultaneous effects of different reference systems on spatial memory. Participants studied a configuration of objects surrounding them. During retrieval, they imagined themselves in the center of the object configuration facing a particular object, and then indicated the directions of other objects relative to this imagined heading. Besides strong effects of egocentric retrieval direction, retrieval was enhanced for objects and headings aligned with an object-centered reference system (triangular object configuration within a neutrally-shaped room), or with a sufficiently salient environmental reference system (triangular room surrounding a neutrally-shaped object configuration). Moreover, remembered object positions were spatially distorted by the object-centered reference system. Results suggest that object positions are accessed by imagining oneself within a topographical representation of objects which is preorganized in terms of both environmental and object-centered reference systems.     

Radial gradient of low-energy (∼0.5–2 MeV) protons at 20–80 AU in the solar activity minima of the 22nd and 23rd cycles

The value of the radial gradient of low-energy (0.5–2 MeV) protons in the heliosphere at distances of 20–80 AU in the periods of solar activity minima in 1985–1987 and 1994–1997 was estimated using the data of the Voyager-1 and Voyager-2 spacecraft (s/c). Preliminary results on the dependence of the radial gradient on the distance were obtained for protons of these energies. The value of the radial gradient varies from –3% (AU)^–1 to –1% (AU)^–1 at distances from the Sun of 20–60 AU, reaching +0.7% (AU)^–1 at maximum considered distances (80 AU). The sign reversal of the proton radial gradient at a distance of 60–70 AU is interpreted as the appearance of a new component: up to the point of inversion there are mainly particles of the solar origin and/or accelerated in the inner heliosphere, while after the reversal of the gradients sign the fluxes of particles prevail whose source is located far from the Sun (maybe in the vicinity of the heliosphere boundary in the region of existence of the termination shock).Translated from Kosmicheskie Issledovaniya, Vol. 43, No. 1, 2005, pp. 3–8.Original Russian Text Copyright © 2005 by Logachev, Zeldovich, Surova.     

Plasma Jet Motion Across the Geomagnetic Field in the “North Star” Active Geophysical Experiment

The active geophysical rocket experiment North Star was carried out in the auroral ionosphere on January 22, 1999, at the Poker Flat Research Range (Alaska, USA) using the American research rocket Black Brant XII with explosive plasma generators on board. Separable modules with scientific equipment were located at distances of from 170 to 1595 m from the plasma source. The experiment continued the series of the Russian–American joint experiments started by the Fluxus experiment in 1997. Two injections of aluminum plasma across the magnetic field were conducted in the North Star experiment. They were different, since in the first injection a neutral gas cloud was formed in order to increase the plasma ionization due to the interaction of neutrals of the jet and cloud. The first and second injections were conducted at heights of 360 and 280 km, respectively. The measurements have shown that the charged particle density was two orders of magnitude higher in the experiment with the gas release. The magnetic field in the first injection was completely expelled by the dense plasma of the jet. The displacement of the magnetic field in the second injection was negligible. The plasma jet velocity in both injections decreased gradually due to its interaction with the geomagnetic field. One of the most interesting results of the experiment was the conservation of high plasma density during the propagation of the divergent jet to considerable distances. This fact can be explained by the action of the critical ionization velocity mechanism.     

INTERBALL-1 Observations of the Kilometric “Continuum” of the Earth's Magnetosphere

The electromagnetic radio-frequency emission of the inner region of the Earth's plasmasphere discovered recently by the GEOTAIL satellite [4] and referred to as the kilometric continuum was observed by the INTERBALL-1 satellite (1995–2000) in the 100–500 kHz band in the AKR-X experiment. During a period of low solar activity (1995–1997), this continuum was found leaving the inner plasmasphere at geocentric distances of 2–4R _E as isolated pencil-like (1°–6°) beams located in the magnetic equator plane. During a time of high solar activity (1999–2000), the occurrence of the emission was extremely rare (it was observed only at a considerable fall of this activity). If detected, at the same geocentric distances (2–4R _E) the continuum demonstrated a strongly variable and perturbed character, as well as a considerably larger extension of the beam over the geomagnetic latitude (10°–20° and more). In addition, quasi-periodic (QP) signals, similar to the observed QP emissions of Jupiter, were sometimes detected in this period. The probable nature of the observed features of the kilometric continuum is briefly discussed.     

NEOs as stepping stones to Mars and main-belt asteroids

Human interplanetary missions are constrained by the problem of astronaut exposure to galactic cosmic radiation. This paper surveys the existing on-line near-Earth object (NEO) data base in an effort to identify NEOs that cross both Earth's ad Mars’ orbits and could be used as cosmic ray shields by interplanetary voyagers. The search concentrated on low-inclination Mars-crossing NEOs that approach Earth, Mars, and main-belt asteroids in the 2020–2100 time frame. Both outbound and return transfers were searched for. Several candidates for Earth–Mars, Mars–Earth, and Earth–Vesta transfers have been found from the very incomplete August 2008 data base. Other aspects of this interplanetary transfer option are considered.     

Effects of stand-off bursts on rubble-pile targets: Evaluation of a hazardous asteroid mitigation strategy

We explore the aftereffects of stand-off burst mitigation on kilometer-scale rubble pile asteroids. We use a simple model of X-ray energy deposition to calculate the impulse transferred to the target, in particular to burst-facing blocks on the target surface. The impulse allows us to estimate an initial velocity field for the blocks on the outer side of the target facing the burst. We model the dynamics using an N-body polyhedron program built on the Open Dynamics Engine, a “physics engine” that integrates the dynamical equations for objects of general shapes and includes collision detection, friction, and dissipation.We tested several different models for target objects: rubble piles with different mass distributions, a “brick-pile” made of closely fitting blocks and zero void space, and a non-spherical “contact binary” rubble pile. Objects were bound together by self-gravity and friction/inelastic restitution with no other cohesive forces. Our fiducial cases involved objects of m=3.5×10¹² kg (corresponding to a radius of 0.7 km for the bulk object), an X-ray yield of 1 megaton, and stand-off burst distances of R=0.8–2.5 km from the target center of mass.Kilometer-scale rubble piles are robust to stand-off bursts of a yield ($Y\sim 1$ megaton) that would be sufficient to provide an effective velocity change ($\mathrm{\Delta }v\sim 0.05\mathrm{m}{\mathrm{s}}^{-1}$). Disaggregation involving some tens of percent of the target mass happens immediately after the impulse; the bulk of the object re-accretes on a few gravitational timescales, and the final deflected target contains over 95% (typically, 98–99%) of the original mass. Off-center components of the mitigation impulse and the target mass distribution cause a small amount of induced spin and off-axis components of velocity change. The off-axis velocity component amounts to an angular deviation of $\sim$ 0.05–0.1 radians from the nominal impulse vector, which may be important for mitigation planning.     

复燃对液体火箭返回阶段底部热环境的影响

为了研究垂直起降液体火箭在返回阶段发动机反向喷流及复燃对箭体着陆支腿和底部热环境的影响,建立了尾焰复燃、流场及光谱辐射计算模型。在国内率先对垂直起降液体火箭在返回阶段的箭体底部热环境进行了数值计算,流场计算采用商业软件,复燃反应使用有限速率化学反应模型;采用HITRAN数据库获得喷流气体组分的光谱吸收系数、正反光线踪迹法求解辐射传递方程。利用文献实验结果,对计算进行了验证并考察了复燃对底部热环境的影响。结果表明:复燃反应对包括箭体底面、侧壁面及着陆支腿的对流和辐射热流密度均会明显升高,最高可达80%以上。因此,研究成果适用于液体火箭返回阶段底部精细化热设计,且在设计过程中有必要考虑复燃的影响。     

Evolution and History in a new “Mathematical SETI” model

In a recent paper (Maccone, 2011 [15]) and in a recent book (Maccone, 2012 [17]), this author proposed a new mathematical model capable of merging SETI and Darwinian Evolution into a single mathematical scheme. This model is based on exponentials and lognormal probability distributions, called “b-lognormals” if they start at any positive time b (“birth”) larger than zero. Indeed:

• 1.Darwinian evolution theory may be regarded as a part of SETI theory in that the factor f_l in the Drake equation represents the fraction of planets suitable for life on which life actually arose, as it happened on Earth.
• 2.In 2008 (Maccone, 2008 [9]) this author firstly provided a statistical generalization of the Drake equation where the number N of communicating ET civilizations in the Galaxy was shown to follow the lognormal probability distribution. This fact is a consequence of the Central Limit Theorem (CLT) of Statistics, stating that the product of a number of independent random variables whose probability densities are unknown and independent of each other approached the lognormal distribution if the number of factors is increased at will, i.e. it approaches infinity.
• 3.Also, in Maccone (2011 [15]), it was shown that the exponential growth of the number of species typical of Darwinian Evolution may be regarded as the geometric locus of the peaks of a one-parameter family of b-lognormal distributions constrained between the time axis and the exponential growth curve. This was a brand-new result. And one more new and far-reaching idea was to define Darwinian Evolution as a particular realization of a stochastic process called Geometric Brownian Motion (GBM) having the above exponential as its own mean value curve.
• 4.The b-lognormals may be also be interpreted as the lifespan of any living being, let it be a cell, or an animal, a plant, a human, or even the historic lifetime of any civilization. In Maccone, (2012 [17, Chapters 6, 7, 8 and 11]), as well as in the present paper, we give important exact equations yielding the b-lognormal when its birth time, senility-time (descending inflexion point) and death time (where the tangent at senility intercepts the time axis) are known. These also are brand-new results. In particular, the σ=1 b-lognormals are shown to be related to the golden ratio, so famous in the arts and in architecture, and these special b-lognormals we call “golden b-lognormals”.
• 5.Applying this new mathematical apparatus to Human History leads to the discovery of the exponential trend of progress between Ancient Greece and the current USA Empire as the envelope of the b-lognormals of all Western Civilizations over a period of 2500 years.
• 6.We then invoke Shannon's Information Theory. The entropy of the obtained b-lognormals turns out to be the index of “development level” reached by each historic civilization. As a consequence, we get a numerical estimate of the entropy difference (i.e. the difference in the evolution levels) between any two civilizations. In particular, this was the case when Spaniards first met with Aztecs in 1519, and we find the relevant entropy difference between Spaniards an Aztecs to be 3.84 bits/individual over a period of about 50 centuries of technological difference. In a similar calculation, the entropy difference between the first living organism on Earth (RNA?) and Humans turns out to equal 25.57 bits/individual over a period of 3.5 billion years of Darwinian Evolution.
• 7.Finally, we extrapolate our exponentials into the future, which is of course arbitrary, but is the best Humans can do before they get in touch with any alien civilization. The results are appalling: the entropy difference between aliens 1 million years more advanced than Humans is of the order of 1000 bits/individual, while 10,000 bits/individual would be requested to any Civilization wishing to colonize the whole Galaxy (Fermi Paradox).
• 8.In conclusion, we have derived a mathematical model capable of estimating how much more advanced than humans an alien civilization will be when SETI succeeds.

     

Revolutionary systems and technologies for missions to the outer planets

The Advanced Deep Space System Development Program is managed by the Jet Propulsion Laboratory for NASA and is also called X2000. X2000 is organized to create advanced flight and ground systems for the exploration of the outer planets and beyond; it has been created to develop the engineering elements of flight and ground systems. Payloads will be developed by another team. Each X2000 delivery gets its requirements from a set of planned missions, or “mission customers”.The X2000 First Delivery Project supports missions to the Sun (to 4 solar radii), Europa (looking for a liquid ocean), Mars (in support of several Mars missions including a sample return), a comet (including a sample return), and Pluto followed by a trip into the Kuiper belt. This set of missions leads to some outstanding requirements:

• 1.1. Long-life (10–12 years)
• 2.2. Total Ionizing Dose of 4 Mrad (for a Europa Orbiter)
• 3.3. Average power consumption less than or equal to 150 Watts
• 4.4. Autonomous operations that result in an extreme reduction in operations costs

This paper describes the X2000 first delivery and its technologies following a brief overview of the program.     

Metallic and Oxidized Aluminum Debris Impacting the Trailing Edge of the Long Duration Exposure Facility (LDEF)

A total of 87 microcraters >30 m in diameter that were found in gold substrates exposed on the trailing edge of the non-spinning Long Duration Exposure Facility (LDEF) yielded analyzable projectile residues in their interiors. Using qualitative SEM-EDS analysis methods, some 60 of these craters were formed by natural cosmic-dust particles, while 27 residues (31%) were assigned to orbital debris (Hörz et al., 1993). The far majority of the orbital-debris impacts, 24 (89%) of the 27 events, contained only aluminum in their X-ray spectra. The present study evaluates these aluminum-rich residues in detail and employs a windowless X-ray detector, which permits for the analysis of low-Z elements and specifically of oxygen. This makes it possible to discriminate between oxidized (Al₂O₃) and metallic (Al) projectiles from dramatically different sources, the former produced during solid-fuel rocket firings, the latter resulting from explosively or collisionally disrupted spacecraft.Of the 24 craters analyzed with the windowless detector, 13 (54%) contained Al₂O₃ and 11 (46%) yielded structurally disintegrated Al metal. The oxidized residues preferentially occur in the smaller craters, all <60 m in diameter. Corresponding particles on LDEF's trailing edge are <35 m in diameter. Some 70% of this particle population is composed of Al₂O₃. Although solid-fuel rocket exhaust products are typically <5 m in size, they tend to coagulate into crusts at the rocket nozzle to be shed occasionally as relatively large, aggregate particles. Structurally disintegrated, metallic fragments compose one-third of all particles <35 m, but they dominate all particles >35 m, and thus all craters >60 m. These findings clearly establish that solid-rocket exhaust particles, as well as explosively or collisionally produced debris, exist in low-inclination, high-eccentricity orbits in sufficient quantities that they must be accounted for in models describing the present and future orbital-debris population at typical Shuttle and Space Station altitudes.     

Path Integration During a Neighborhood Walk

In three experiments, we contrast two accounts of path integration processes that track direction and distance of movement. Moment-to-moment updating involves the continuous sensing of motion; automatic calculations constantly produce an estimate of position and orientation of self to an anchor point for travel. In contrast, configural updating can be accomplished using episodic memories; a representation of the traveled path is periodically revised and the bearing to the origin of a route can be estimated by connecting the endpoint of the current leg to the starting point of the first leg. Experiments 1 and 3 indicate that people encode the number and direction of turns but have difficulty configuring more gradually curved legs. In Experiment 2, we find that blindfolded people show better than chance performance in estimating the origin of outdoor routes when they are unexpectedly asked to point. It appears that, in addition to episodic memories that allow configural updating, we have available a moment-to-moment representation of our position and heading based on the cues that accompany self-movement.     

Study of Micrometeoroid and Orbital Debris Effects on the Solar Panels Retrieved from the Space Station “MIR”

A study of micrometeoroid and orbital debris (MMOD) long-term effects on solar cell samples of solar panels returned from the space station MIR has been carried out. Five samples from the solar array, which spent over 10 years in space, have been studied with the help of optical microscopes with magnification up to 1000. Craters with dimensions as small as 1m were registered. Additional large impact features were investigated by observing a large number of cells (150) with an optical microscope of small magnification. The aim of the study was to define morphological and statistical characteristics of samples surface damages as well as the extent of surface erosion caused by MMOD impacts. The results of statistical analysis of the data obtained in this study are shown to correlate with the experimental data obtained in the Hubble Telescope solar panel return experiment, and MMOD flux estimations are in good agreement with modern MMOD models. The relative surface area damaged by impacts of small size (1–100m) MMOD particles is estimated to be 0.01%, while the relative surface area of large impact features (greater than 0.1mm) is estimated to be 0.045%.     

Observations of electromagnetic emissions inside the Earth’s plasmasphere from the <Emphasis Type="Italic">Interball-1</Emphasis> satellite

The spectrum analyzer AKR-X onboard the Interball-1 satellite at the beginning (August–October 1995) and at the end (August–October 2000) of satellite operation in perigees of its orbital motion recorded and analyzed electromagnetic emissions of the inner regions of the Earth’s plasmasphere in the frequency band 100–1500 kHz at distances of 1.1–1.8 R _E. The observations have shown that the electromagnetic modes (the Z and LO modes escaping the magnetosphere) which are formed at the altitudes 600–4000 km are associated with the subauroral nonthermal continuum and with the recently discovered kilometric continuum. There are noticeable differences in the spectral character of these emissions during the minimum (1996) and maximum (2000) solar activity, when, as a rule, the LO mode escaping the plasmaphere and the continua are not present.